The invention is directed generally to machinery, and more particularly to a line transfer system with a contour machining head.
Machining of materials to create openings or recesses of different shapes is used in the manufacture and repair of a wide range of objects. In applications where the dimensional tolerances, roundness and smoothness of the machined surface are important, special tools are often required, especially when the material to be machined is very hard or otherwise difficult to machine. For example, transfer machines within an automated manufacturing line often require multiple machining heads with a variety of different cutting bits to form rounded openings of the desired profiles. The more different machining heads required in a transfer machine, the more complex the machine becomes, and the more floor space it requires. As an alternative to multiple machining heads, a single cutting machine can be adapted to receive a variety of different cutting bits. However, when the cutting bit needs to be changed, the processing line must be paused or shut down, resulting in reduced throughput.
In an exemplary application, such cutting tools are used in the repair of the cylinders heads of internal combustion engines to re-establish the high quality seal required for efficient engine performance and fuel consumption. It is well known among vehicle mechanics that valve seats can be machined to remove the outer surface of the seat to expose a smooth and uniform contact surface by a technique commonly referred to as xe2x80x9clappingxe2x80x9d. This lapping technique is accomplished by removing the cylinder head from the engine and machining the valve seats with a cutting blade. Typically, a valve seat has a profile with three different angles: a throat angle, a valve seat angle, and a top angle. In order to simultaneously cut the different angles, a xe2x80x9cthree-anglexe2x80x9d cutting blade or bit is used. Each cutting edge of the three-angle cutting bit corresponds to one of the valve seat angles to be machined. Three-angle cutting bits vary in size and shape depending on the type of cylinder head valve seat being machined. These three-angle cutting bits are currently used by valve seat and guide manufacturers.
A disadvantage of the lapping technique is the risk of damage to the surface finish from vibration, chattering, or undulation generated by flexion of the cutting bits. This problem develops because certain cylinder head valve seat shapes require a three-angle cutting bit with a long cutting edge. Rotation of this long cutting edge when the edge is in contact with the work surface can create flexions in the cutting bit, especially when the material is difficult to machine, i.e., a very hard material. These flexions generate vibrations, chattering, or undulations which can disrupt contact between the cutting edge and the surface being cut. The skipping blade can damage the surface finish of the valve seat resulting in a machined valve seat that is not acceptable by Original Equipment Manufacturer (OEM) standards.
Another disadvantage of the lapping technique is a decentering phenomena. As stated above, cutting efforts with a long cutting edge/surface create flexions. These flexions create an unbalanced radial cutting effort which decenters the three-angle cutting blade, also resulting in unacceptable quality.
Still another disadvantage of the lapping technique is the large number of three-angle cutting blades needed to machine different types of valve seats. Each type of engine has a different valve seat profile. Thus, one or more unique three-angle cutting blades may be needed for each type of engine.
Finally, many conventional cutting machines operate at high rotational speeds with numerous moving parts. Numerous moving parts rotating at high speeds can cause weight imbalances within a conventional cutting machine, adversely affecting the stability of the cutting machine and potentially affecting the precision cutting operations of the cutting machine. Thus, there is a need for a precision cutting machine that can operate at high rotational speeds while compensating for the weight of its numerous moving parts.
Furthermore, conventional cutting machines lack the capability to perform a variety and wide range of cutting operations needed to simultaneously form complex lines and shapes in one or more workpieces in a relatively efficient manner. Thus, there is a need for a precision cutting machine that can be adjusted to perform a variety and wide range of cutting operations needed to simultaneously form complex lines and shapes in one or more workpieces in a relatively efficient manner.
Moreover, in a conventional cutting machine, a pilot may be used to guide or center a cutting blade or tip with respect to the workpiece. For example, a pilot can be inserted into a valve guide in order to align the bit tool with the valve seat to be machined. When needed, the pilot may be changed by an operator according to the size or configuration of the workpiece to be machined. In some instances, a pilot is secured to the cutting machine by a deformable hydraulic sleeve system. A screw actuated by an operator pushes a piston which, in turn, compresses oil trapped in a chamber. The chamber includes a membrane sleeve that surrounds and wraps around the pilot shank. As the oil pressure increases in the membrane sleeve, the pressure applies inward compression on the pilot shank from all directions, firmly holding the pilot shank in place. To change the pilot, the screw must be manually loosened to relieve the pressure in the membrane sleeve, and then the pilot can be removed. However, replacing the pilot in a conventional cutting machine can be rather difficult and time consuming since the screw must be manually adjusted by an operator to properly tension and untension the screw to secure and release the pilot. In some instances, the operator may fail to properly tension or untension the screw to secure or release the pilot, thus wasting time. Therefore, a need exists for a cutting machine with an apparatus that permits a pilot to be changed in an efficient manner.
Further, in a cutting operation with a conventional cutting machine, the insertion of a pilot within a valve guide or other guide bore is typically a manually performed operation. For example, usually an operator of a cutting machine visually locates a valve guide, and then manually aligns the pilot of the cutting machine with the valve guide. When the pilot and valve guide are aligned, the operator manually lowers and inserts the pilot into the valve guide prior to machining the workpiece. This manually performed operation can be time consuming and inefficient for operators if the alignment is not properly performed the first time, or if the operator lacks coordination, experience or skill in aligning a pilot with a valve guide or other guide bore.
In the case of a fully automated (numerically controlled axis), i.e. a machine with all the movements of the head controlled by motors, the automated insertion of the pilot within valve guides or other guide bores presents other difficulties. For example, in order to insert a pilot within a valve guide, the pilot must be aligned precisely with the valve guide, with a precision leveling device within a micron tolerance, both in the x and y axes. When the machining head of the cutting machine is moved manually by an operator who can visually locate the valve guide, the alignment occurs naturally, xe2x80x9cby itselfxe2x80x9d, since the machining head is free to align itself with the pilot. However, in the case of automated movement, the system controller and motors do not know where, exactly, the valve guide is located. This problem is compounded by the fact that the positioning tolerance of a valve guide in a cylinder head is typically within 0.1 mm or less. Other valve guides or guide bores tolerances will have similar requirements.
Once the tip of the pilot has been engaged within the valve guide, it is critical to be able to continue the downward movement to insert the pilot fully within the valve guide. This is another problem since the valve guide is not necessarily vertical, while the downward movement of the pilot is perfectly vertical. In fact, the valve guide may not even be straight. Therefore, there is a need for a cutting machine with an apparatus that permits a pilot to be aligned with a workpiece in an efficient manner.
Finally, in a cutting operation with a conventional cutting machine, an operator may want to assess the quality of the cutting operation with a particular bit tool. For example, an operator performing a valve seat machining operation may want to assess whether the valve seat profile has been fully and properly cut. If the cutting effort by the bit tool is too great, i.e., creating a significant amount of strain on the bit tool, the cutting machine may automatically stop to prevent breakage of the bit tool or cutting machine. Such an instance might be where the bit tool is encountering excessive resistance due to the hardness of the workpiece material. Alternatively, if the cutting effort by the bit tool is insufficient, the cutting machine may automatically add additional machining cycles until the cutting operation has been completed according to predetermined parameters. Thus, there is a need for a cutting machine that determines the quality of a cutting operation with a particular bit tool.
In view of the aforementioned inadequacies of the prior art, the need exists for cutting tools and methods for machining rounded openings that produce a precision quality finish and use a universal bit tool.
It is an advantage of the invention to provide a universal cutting bit and bit holder having the ability to rapidly and precisely machine a wide range of openings or recesses of varied shapes and/or profiles.
It is also an advantage of the invention to substantially reduce flexion of the cutting bit during machining.
It is another advantage of the invention to eliminate de-centering phenomena due to unbalanced radial efforts from flexion, and to eliminate concentricity defects resulting from cutting/machining effort.
Yet another advantage of the invention is to eliminate vibrations, chattering, and undulations to provide improved finish for the machined surface.
Still another advantage of the invention is to provide concentric machining for multiple contours within a opening.
Another advantage of the invention is to provide a precision cutting machine that can operate at high rotational speeds while compensating for the weight of its numerous moving parts.
Yet another advantage of the invention is to provide a precision cutting machine that can be adjusted to perform a variety and wide range of cutting operations needed to simultaneously form complex lines and shapes in a workpiece in a relatively efficient manner.
Yet another advantage of the invention is to permit a pilot of a cutting machine to be changed in an efficient manner.
Another advantage of the invention is to permit a pilot of a cutting machine to be aligned with a workpiece in an efficient manner.
Finally, an advantage of the invention is to determine the quality of a cutting operation with a particular bit tool.
In an exemplary embodiment, the invention is a line transfer system with a contour machining head for machining a workpiece. A line transfer system with a contour machining head comprises a driving system with a z-axis adjustable spindle, a depth gauge, a pilot, a contour machining head, and a system controller. The line transfer system with at least one contour machining head includes a spindle, a carriage head, a carriage head holder, a carriage feed driving assembly, and a universal cutting blade. A fixed pilot is attached to the bottom of the carriage head along the z-axis of a machine spindle to provide a means for centering the machining head in the opening to be machined, e.g., a valve guide of a cylinder head. The carriage head holder attaches to an extension of the machine spindle so that when the machine spindle is rotated, the machining head rotates. The carriage head is attached to the carriage head holder at an inclined angle relative to the bottom surface of the carriage head. The carriage feed driving assembly provides control of the inward and outward movement of the carriage head. The universal cutting blade is mounted on the carriage head through one of a plurality of mounting holes. For applications to cylinder head repair, the machining head can be utilized with virtually any conventional valve seat machining system, but is preferably used with the systems disclosed in U.S. Pat. Nos. 5,613,809, 5725,335, and 5,829,928 of Harmand, et al. (hereinafter the ""809, ""335, and ""928 patents, respectively) which are incorporated herein by reference.
The machining apparatus of the exemplary embodiment comprises a driving system, a machining head as described above, a pilot, a depth gauge, and a system controller. The driving system further comprises a machining sphere, a machine spindle, a spindle sheath, a rotational drive motor, and a vertical displacement motor. The spindle sheath is disposed within and supported by the machine sphere. The spindle sheath is fixed within the x- and y-axis, but can move along the z-axis by the vertical displacement motor. The vertical displacement motor is electrically connected and controlled by the system controller. The machine spindle is disposed within the spindle sheath and rotates around its z-axis through a drive motor. The drive motor rotating the machine spindle is electrically connected to and controlled by the system controller. The depth gauge is disposed on the spindle sheath by a fixed arm and is electrically connected to the system controller. The depth gauge measures the distance between a top surface of a cylinder head and the cutting blade. In a preferred embodiment, a second vertical displacement motor is provided so that feed of the arbor, which controls the carriage feed rate, is independent of the spindle feed which vertically moves the spindle, housing and all components therein relative to the working surface, providing three independent degrees of motion.
The system controller includes a memory which contains software for controlling the operation of the cutting tool. This system controller includes a user interface such as a touch screen at which an operator can input the parameters that define the geometry of, for example, a valve seat profile. These parameters are used by the system controller to determine the vertical feed rate of the contour machining head, the length of the vertical displacement of the contour machining head to machine the segment, the inward/outward displacement of the carriage head, and the number of rotations needed to machine a segment of the valve seat profile. The system controller uses a look-up table, stored externally or within internal memory, and the input information is used to determine the vertical feed rate of the machine spindle, the length of the vertical displacement of the spindle to machine the segment, and the number of rotations needed to machine a segment of the valve seat profile. An operator simply centers the spindle, activates the system after the initial input of information for a given cylinder head and valve seat profile, and re-centers on each subsequent valve seat before activation.
For applications to transfer machines or other machining applications, the system controller coordinates operation of the machining head with the transfer of work pieces into a work station associated with the machining head. As with the embodiment for use for valve seat machining, the controller stores data including the parameters used to control the machining head to achieve the desired characteristics (profile, diameter, depth, finish smoothness, etc.) of the opening. The data may be entered via a user interface located at a central controller within the transfer line, or may be located at the locating at which the machining is to occur.
At least three aspects of the invention relate to means for automating operation of the machines such as to allow operation with little or no human supervision and interaction.
A first aspect of the invention includes the use of robot arms for automated changing of tools such as pilots and reamers into the contour machining head.
A second aspect of the invention provides xe2x80x9cintelligencexe2x80x9d to the machine in a way that allows it to determine the amount of machining effort being exerted and making adjustments as needed.
Yet another aspect of the invention permits the machine to automatically insert the pilot in the valve guide or other guide hole by controlling movement in the horizontal plane and the approach angle.
The invention described herein provides a number of improvements to the xe2x80x9cContour Machining Headxe2x80x9d disclosed in pending patent application Ser. No. 09/828,543, filed Apr. 6, 2001, published Aug. 30, 2001 as Publication No. U.S. 2001/0018012 A1, which is incorporated herein in its entirety by reference. The following improvements described and illustrated in the accompanying figures are not intended to be limited to use in conjunction with the xe2x80x9cContour Machining Headxe2x80x9d described in the referenced application or with the commercial embodiment of that machine, sold under the names xe2x80x9cContour-1685xe2x80x9d and xe2x80x9cContour Epochxe2x80x9d by Newen, Inc. of San Diego, Calif. Rather, the improvements may be incorporated in any similar machine. Furthermore, methods and processes described and illustrated in the accompanying specification may be sold under the names xe2x80x9cFixed Turningxe2x80x9d and/or xe2x80x9cSingle Point Cuttingxe2x80x9d.